CN115668645A - Waveguide tube slit antenna - Google Patents

Abstract

A waveguide slot antenna according to an aspect of the present disclosure includes: a waveguide (10) that is provided with a plurality of slits (6) that are provided at predetermined intervals in the central axis direction and that serves as a radiation unit (8) that radiates radio waves; and a concave-convex section (20) provided on the outer wall surface (4) around the radiation section so as to periodically spread from the radiation section. The concave-convex portion is configured to reflect an incident wave of the radio wave from the radiation portion, which is incident from the front in the radiation direction, in a direction different from the incident direction of the incident wave.

Description

still pipe slot antenna

Cross References to Related Applications

This international application claims the priority of Japanese Patent Application No. 2020-90692 filed with the Japan Patent Office on May 25, 2020, the entire contents of which are incorporated herein.

technical field

The present disclosure relates to a waveguide slot antenna having a waveguide in which a plurality of slits are provided on a side surface at predetermined intervals.

Background technique

As described in Patent Document 1, there is known a frequency selective surface unit capable of suppressing unnecessary reflection of radio waves from an antenna device. The frequency selective surface unit is formed by providing a cross-shaped annular slit formed by a copper mesh layer having a cross-shaped slit and a cross-shaped copper strip layer arranged in the slit of the copper mesh layer on a dielectric substrate. .

According to this frequency selective surface unit, by adjusting the size of the cross-shaped annular slit, transmission and reception of radio waves by the antenna device can be performed, and reflection of the radio waves from the antenna device can be suppressed.

On the other hand, as an antenna device used in a radar device or a communication device, there is known a waveguide slot antenna having a waveguide in which a plurality of slits are provided on the side surface at predetermined intervals. In this waveguide slot antenna, the periphery of the slot is metal, so if an object such as a radome is placed in front of the radiation direction of the radio wave, the transmitted radio wave will be reflected by the object and reach the metal part around the slot. Metal parts are reflected with low loss. Therefore, in the waveguide slot antenna, superimposed reflection may occur between an object such as a radome arranged in front of the radio wave radiation direction and the metal part of the antenna body.

Patent Document 1: CN102723541B.

In the waveguide slot antenna, if overlapping reflections of radio waves occur, the reflected waves caused by the overlapping reflections interfere with the reflected waves from the object to be detected in the radar device, or interfere with the reflected waves transmitted from the communication target in the communication device. incoming radio interference. Therefore, superimposed reflection in the still-pipe slot antenna becomes an important factor in deteriorating the object detection performance of the radar device and the communication performance of the communication device.

On the other hand, according to the frequency selective surface unit described in Patent Document 1, reflection of radio waves can be suppressed. Therefore, if the frequency selective surface unit described in Patent Document 1 is arranged in front of the radiation direction of the waveguide slot antenna, the above-mentioned superimposed reflection can be suppressed, and performance degradation of a radar device or a communication device using the antenna can be suppressed.

However, as a result of detailed studies by the inventors, it was found that in the frequency selective surface unit described in Patent Document 1, the frequency of radio waves that can be suppressed from reflection is limited by the cross-shaped annular slit, so that the frequency of radio waves that can be transmitted and received Issues such as narrowing of the frequency band.

In addition, the frequency selective surface unit described in Patent Document 1 is arranged as a so-called filter in front of the radio wave radiation direction of the waveguide slot antenna, so it also attenuates transmitted and received radio waves, and radar devices, communication devices, etc. There is such a problem that the performance of the device decreases.

Contents of the invention

One aspect of the present disclosure desires that, in the waveguide slot antenna, it is possible to suppress superimposed reflections that occur between objects placed in front of the radiation direction of radio waves and the antenna main body without using a filter such as a frequency selective surface element.

A waveguide slot antenna according to a first aspect of the present disclosure includes a waveguide including a plurality of slits arranged at predetermined intervals in the central axis direction. The plurality of slits provided in the waveguide function as radiation portions that radiate radio waves.

In addition, concavo-convex portions are provided on the outer wall surface around the radiation portion so as to periodically extend from the radiation portion. The concavo-convex portion is configured to reflect an incident wave incident from the front of the radiation direction of the radio wave from the radiation portion in a direction different from the incident direction of the incident wave.

Therefore, according to the waveguide slot antenna of the present disclosure, when the radio wave radiated from the radiating part collides with an object arranged in front of the radiation direction and reflects it, and when the reflected wave enters the antenna device, the direction of the incident wave and the direction of the incident wave can be adjusted. reflections in different directions.

Therefore, it is possible to suppress the occurrence of the above-mentioned superimposed reflection by reflecting waves from an object disposed forward in the radiation direction from the outer wall surface around the radiation portion toward the object.

Thus, according to the waveguide slot antenna of the present disclosure, it is possible to suppress unnecessary noise components from being superimposed on radio waves that should be transmitted and received by the waveguide slot antenna due to superimposed reflection, and to use the waveguide slot antenna. The performance of the radar device and communication device is degraded.

In addition, according to the waveguide slot antenna of the present disclosure, it is not necessary to arrange a filter such as the above-mentioned frequency selective surface unit in front of the radiation direction of radio waves in order to suppress overlapping reflections. Therefore, it is possible to suppress the narrowing of the frequency band of radio waves that can be transmitted and received by the waveguide slot antenna or the reduction in the transmission and reception power of the radio waves by disposing a filter such as a frequency selective surface unit.

Next, a waveguide slot antenna according to a second aspect of the present disclosure is constituted by a waveguide including a plurality of slits provided at predetermined intervals in the direction of the central axis as radiation portions that radiate linearly polarized radio waves.

Further, a plurality of linear protrusions are provided at intervals on the outer wall surface around the radiation portion so as to be inclined at a predetermined angle with respect to the central axis of the waveguide.

The plurality of ridges are configured to reflect an incident wave of radio waves from the radiating portion that enters from the front in the radiation direction through each ridge and the groove portion sandwiched by the ridge so that the polarization plane of the incident wave is rotated by a predetermined angle. .

Therefore, according to the waveguide slot antenna of the present disclosure, it is possible to suppress a situation in which linearly polarized radio waves radiated from the radiating portion are overlapped and reflected between an object arranged in front of the radiating direction and the outer wall surface around the radiating portion and enter In the case of the radiation section, the incident wave is received by the radiation section.

Accordingly, in the waveguide slot antenna of the present disclosure, it is possible to suppress performance degradation of a radar device or a communication device using the waveguide slot antenna due to the above-mentioned superimposed reflection.

Also, in the waveguide slot antenna of the present disclosure, there is no need to arrange a filter such as a frequency selective surface element in front of the radio wave radiation direction. Therefore, it is possible to suppress the narrowing of the frequency band of radio waves that can be transmitted and received or the reduction of the transmission and reception power of the radio waves.

Description of drawings

FIG. 1 is a perspective view showing the overall configuration of an antenna device according to a first embodiment.

FIG. 2 is an explanatory diagram illustrating an arrangement state of a plurality of waveguides constituting the antenna device.

FIG. 3 is an explanatory diagram illustrating superimposed reflections occurring between the antenna device and an object.

FIG. 4 is an explanatory diagram illustrating the shape of the concave-convex portion and the reflection of radio waves by the concave-convex portion.

FIG. 5A is an explanatory diagram showing the radio wave reflection characteristics of the antenna device having no concavo-convex portion.

5B is an explanatory diagram showing the radio wave reflection characteristics of the antenna device according to the first embodiment.

6 is a perspective view showing the overall configuration of an antenna device according to a first modified example.

7 is a perspective view showing the overall configuration of an antenna device according to a second modified example.

8 is a perspective view showing the overall configuration of an antenna device according to a third modified example.

9 is a perspective view showing the overall configuration of an antenna device according to a fourth modification example.

10 is a perspective view showing the overall configuration of an antenna device according to a second embodiment.

FIG. 11 is an explanatory diagram for explaining the reflection characteristics of radio waves by protrusions and grooves according to the second embodiment.

FIG. 12A is an explanatory diagram showing the radio wave reflection characteristics of an antenna device having no concave and convex portions.

FIG. 12B is an explanatory diagram showing the radio wave reflection characteristics of the antenna device according to the second embodiment.

Detailed ways

Embodiments of the present disclosure will be described below with reference to the drawings.

[first embodiment]

The waveguide slot antenna of the present embodiment is used, for example, as an antenna device for transmitting and receiving millimeter waves in a frequency band of 70 to 80 GHz in a millimeter wave radar device mounted on an automobile or the like. Therefore, in the following description, the waveguide slot antenna of the embodiment is only referred to as the antenna device 2 .

The antenna device 2 of the present embodiment shown in FIG. 1 includes a plurality of waveguides 10 arranged in the X-axis direction of the outer wall surface 4 along the outer wall surface 4 perpendicular to the Z-axis direction as a radiation direction of radio waves.

The plurality of waveguides 10 are made of metal, and as shown in FIG. parallel.

In addition, a plurality of slits 6 are provided in each of the plurality of waveguides 10 at predetermined intervals in the central axis O direction of the waveguide 10 . Therefore, since the waveguides 10 are arranged in parallel, the slits 6 are arranged at predetermined intervals in the X-axis direction and the Y-axis direction on the outer wall surface 4 of the antenna device 2 .

In this way, the plurality of slits 6 dispersedly arranged in the X-axis direction and the Y-axis direction function as radiation portions 8 that radiate radio waves from the outer wall surface 4 of the antenna device 2 to the Z-axis direction.

In addition, in each waveguide 10, the plurality of slits 6 are elongated in the direction of the central axis O of the waveguide 10, and in the direction of the central axis O of the waveguide 10, each slit 6 is formed by the antenna device 2. It is arranged to transmit and receive one-half (λ/2) of the wavelength λ of the center frequency of radio waves.

In addition, in each waveguide 10 , a plurality of slits 6 are alternately arranged at positions eccentric from the central axis O across the central axis O of the waveguide 10 . This is to prevent the radio waves radiated from the slits 6 from inversion and cancellation.

Next, in the antenna device 2, a high-frequency signal transmission path, a detector, etc. are provided around the above-mentioned plurality of waveguides 10, so as to input a transmission signal to each waveguide 10 or extract a signal from the waveguide 10. receive signal.

In addition, the configuration of the waveguide 10 in which a plurality of slits 6 are provided as described above, the method of feeding power to the waveguide 10, etc., are well-known technologies such as those described in Japanese Patent Application Laid-Open No. 2008-167246, etc., so details are omitted here. instruction of.

Furthermore, the outer wall surface 4 of the antenna device 2 extends from the plurality of waveguides 10 in the X-axis direction in order to arrange a transmission path and a probe for high-frequency signals in the antenna device 2 . In addition, the outer wall surface 4 around the waveguide 10 is made of the same metal as the waveguide 10 .

In addition, as shown in FIG. 1 , in the antenna device 2 , the outer wall surface 4 around the radiation portion 8 is provided so as to surround the radiation portion 8 from both sides in the X-axis direction. Concave-convex portion 20 that expands.

The concavo-convex part 20 is for reflecting the radio wave radiated from the radiation part 8 in a direction different from the incident direction when the radio wave radiated from the radiation part 8 collides with an object arranged in front of the radiation direction of the radio wave and reflects it, and the reflected wave enters the antenna device 2 .

In other words, by installing the antenna device 2 in the car so that the X-axis direction of the plurality of waveguides 10 is arranged horizontally, the radar device can be used to detect other vehicles, pedestrians, etc. located ahead of the car in the direction of travel. object mark.

In addition, as shown in FIG. 3 , an object 50 such as a bumper of a car or a radome protecting the antenna device 2 is disposed forward in the radiation direction of radio waves from the radiation portion 8 of the antenna device 2 . Therefore, the radio waves radiated from the radiator 8 pass through the object 50 to radiate around the vehicle, and part of the radio waves are reflected by the object 50 , and the reflected waves enter the antenna device 2 .

In addition, the outer wall surface 4 of the antenna device 2 is made of the same metal as the waveguide 10, so the incident wave reflected by the object 50 and incident on the antenna device 2 is reflected by the outer wall surface 4 of the antenna device 2 with low loss.

As a result, superimposed reflection in which a part of radio waves radiated from the antenna device 2 is repeatedly reflected between the object 50 and the outer wall surface 4 occurs. Furthermore, when such superimposed reflections occur, unnecessary signal components due to superimposed reflections are superimposed on the reception signal of the antenna device 2 , so that the detection accuracy of the target object by the radar device is lowered.

Therefore, in the present embodiment, in order to suppress the overlapping reflection, the concave-convex portion 20 is provided on the outer wall surface 4 around the radiation portion 8 .

The concavo-convex portion 20 includes a plurality of protrusions 22 linearly formed parallel to the central axis O of the waveguide 10 in which the plurality of slits 6 are arranged, and grooves 24 sandwiched between the protrusions 22 and the protrusions 22 . .

In addition, as shown in FIG. 4, in the concavo-convex portion 20, the widths in the arrangement direction of the protrusions 22 and grooves 24 periodically arranged in the X-axis direction are set to the wavelengths of the radio waves transmitted and received by the antenna device 2 ( 1/2 (λ/2) of λ).

As a result, the reflected waves radiated forward in the Z-axis direction from the radiation portion 8 and reflected from the object 50 located forward in the radiation direction are respectively reflected on the outer wall surfaces of the protrusion 22 as a convex portion and the groove portion 24 as a concave portion, However, a phase difference occurs in the reflected wave according to the depth H of the groove portion 24 .

And, due to this phase difference, the reflected wave reflected from the outer wall surface 4 of the antenna device 2 is reflected in a direction different from the incident direction from the object 50 arranged in front of the radiation direction.

In other words, the reflected wave from the object 50 arranged in front of the radiation direction enters the outer wall surface 4 of the antenna device 2 from the Z-axis direction, but the incident wave is different from the incident angle of the incident wave as shown by the hollow arrow in FIG. 4 . The angle of is reflected from the outer wall surface 4 of the antenna device 2 .

Therefore, the power of the reflected wave reflected from the outer wall surface 4 of the antenna device 2 toward the object 50 forward in the radiation direction is significantly lower than that of an antenna device without the concave-convex portion 20 , and superimposed reflection can be suppressed.

For example, FIG. 5A shows the measurement results of the reflected power of radio waves measured in the antenna device with no concave-convex portion 20 on the outer wall surface 4, and FIG. Power measurement results.

In addition, this measurement result shows the reflected power of the radio wave when the reflection angle changes on the XZ plane and the YZ plane, using the Z-axis direction as a reference angle 0 [deg.].

As shown in FIG. 5A, in the antenna device having no concave-convex portion 20 on the outer wall surface 4, the reflected power relative to the incident wave incident from the Z-axis direction is maximum in the Z-axis direction at a reflection angle of 0 [deg.], and increases with the reflection angle It decreases in the X-axis direction and the Y-axis direction.

On the other hand, in the antenna device 2 of the present embodiment, as shown in FIG. 5B , the reflected power is greatly reduced in the range of the reflection angle 0±40 [deg.] compared to the antenna device without the concave-convex portion 20 . This is because incident waves are dispersedly reflected in the X-axis direction by the concavo-convex portion 20 .

Thus, according to the antenna device 2 of this embodiment, when a reflected wave from an object 50 arranged in front of the radio wave radiation direction enters the antenna device 2 , the incident wave can be dispersedly reflected in a direction different from the incident direction.

Therefore, even if the radio wave radiated from the radiating portion 8 of the antenna device 2 is reflected by the object 50 arranged in front of the radiation direction, and the reflected wave enters the antenna device 2, it is possible to suppress the occurrence of radio waves between the outer wall surface 4 of the antenna device 2 and the object 50. overlapping reflections.

Thus, according to the antenna device 2 of the present embodiment, it is possible to reduce unnecessary reflected signal components received by the radiation unit 8 due to superimposed reflection, and to improve the detection accuracy of the target object by the radar device.

In addition, in the antenna device 2 of this embodiment, it is not necessary to provide a filter such as a frequency selective surface unit in order to suppress the occurrence of overlapping reflections, so it is possible to suppress the narrowing of the frequency band of radio waves that can be transmitted and received, and suppress the transmission of the radio waves. A situation where the received power is reduced.

In addition, the reflection direction of the radio wave from the outer wall surface 4 of the antenna device 2 can be set by adjusting the phases of the reflected waves from the protrusion 22 and the groove portion 24 according to the depth H of the groove portion 24. 22 width to set the reflection direction.

In other words, if the width of the protrusion 22 is made larger than λ/2, the reflected power from the protrusion 22 increases, and if the width of the protrusion 22 is made smaller than λ/2, the reflected power from the protrusion 22 decreases. Therefore, by adjusting the width of the protrusion 22, the reflected power from the protrusion 22 can be adjusted.

Furthermore, by adjusting the reflected power from the protrusion 22 , it is possible to change the reflection direction of the reflected wave combined with the reflected wave from the groove portion 24 and reflected from the outer wall surface 4 of the antenna device 2 .

Therefore, the width of the protrusion 22 does not necessarily need to be set to λ/2, and may be appropriately set according to the reflection direction of the wave reflected from the outer wall surface 4 .

In addition, as for the groove portion 24, it is only necessary that radio waves enter the groove portion 24 and reflect the incident wave on the outer wall surface inside the groove portion 24, so the width of the groove portion 24 may be larger than λ/2. In other words, if the width of the groove portion 24 is made smaller than λ/2, it is considered that radio waves cannot be incident into the groove portion 24 and the radio waves cannot be reflected. However, if the width of the groove portion 24 is made larger than λ/2, Then, the radio waves incident on the antenna device 2 can be reflected by the groove portion 24 .

Therefore, in the antenna device 2 of the present embodiment, by appropriately adjusting the widths of the protrusions 22 and the grooves 24 in the concave-convex part 20, and the depth H of the grooves 24, it is possible to arbitrarily set the height from the outside of the antenna device 2. The reflection direction of the radio waves on the wall 4. Furthermore, by setting these parameters, it is possible to further improve the detection accuracy of the target object in the radar device.

In addition, it is not necessary to make the depth H of the groove portion 24, in other words, the heights of the protrusions 22 all the same. The height of each protrusion 22 is set to a different height.

In addition, in the present embodiment, the plurality of slits 6 provided in the waveguide 10 are elongated, and each slit 6 is provided in the waveguide so that the longitudinal direction of each slit 6 is in the direction of the central axis O of the waveguide 10 . The tube 10, so the antenna device 2 transmits and receives linearly polarized radio waves.

However, the waveguide slot antenna of the present disclosure may be, for example, an antenna device configured such that the slot 6 is cross-shaped and transmits and receives circularly polarized radio waves. In other words, even in the antenna device for transmitting and receiving circularly polarized radio waves, the same effect as above can be obtained by providing the concave-convex portion 20 around the radiation portion 8 as described above.

[First modified example]

Here, in the above-mentioned first embodiment, the concavo-convex portion 20 is composed of a plurality of protrusions 22 arranged at intervals in the X-axis direction in a straight line parallel to the central axis O of the waveguide 10, and the protrusions 22 are sandwiched between the protrusions 22 and the The case where the groove part 24 between the protrusions 22 is comprised is demonstrated as an example.

On the other hand, in the antenna device 2 of the first modified example, as shown in FIG. 6 , the concavo-convex portions 20 are distributed and arranged at predetermined intervals in the X-axis direction and the Y-axis direction so as to surround the radiation portion 8 . a plurality of protrusions 26; and the groove portion 24 sandwiched by the protrusions 26.

Even if the concave-convex portion 20 is configured in this way, if the width of the protrusion 26 and the groove portion 24 and the depth of the groove portion 24 are set in the same manner as in the above-mentioned embodiment, the radio wave from the outer wall surface 4 around the radiation portion 8 can be transmitted The reflection direction is set to an arbitrary direction different from the Z-axis direction.

Therefore, also in the antenna device 2 of this modified example, as in the above-mentioned first embodiment, overlapping reflections between the outer wall surface 4 of the antenna device 2 and the object 50 arranged forward in the radiation direction can be suppressed.

In addition, in this modified example, the protrusions 26 constituting the concavo-convex portion 20 have a square prism shape, but the protrusions 26 may be triangular or pentagonal or larger prism shapes, or may be circular or elliptical cylindrical shapes.

In addition, it is not necessary to make all the protrusions 26 have the same shape, and the protrusions 26 having different shapes may be appropriately dispersed and arranged. In addition, it is not necessary to make the heights of the protrusions 26 from the groove portion 24 all the same, and each protrusion 26 or each protrusion 26 may have different heights.

In addition, in this modified example, the protrusions 26 are arranged at constant intervals in the X-axis direction and the Y-axis direction, but the intervals and arrangement directions may be set arbitrarily, for example, from the center of the radiation portion 8 Arranged radially.

[Second modified example]

As shown in FIG. 7 , in the antenna device 2 of the second modified example, the concavo-convex portion 20 is formed of a plurality of ring-shaped protrusions so as to surround the entire area around the radiation portion 8 constituted by the plurality of slits 6 . 28 , and the annular groove 24 sandwiched by the protrusions 28 .

Even if the concavo-convex portion 20 is configured in this way, if the width of the annular protrusion 28 and the groove portion 24 and the depth of the groove portion 24 are set in the same manner as in the above-mentioned embodiment, the The reflection direction of the radio wave on the outer wall surface 4 is set to an arbitrary direction different from the Z-axis direction.

Therefore, also in the antenna device 2 of this modified example, as in the first embodiment and the first modified example described above, it is possible to suppress the occurrence of overlapping between the outer wall surface 4 of the antenna device 2 and the object 50 arranged forward in the radiation direction. reflection.

In addition, although in this modified example, the protruding bar 28 constituting the concave-convex part 20 is made into an annular shape, the protruding bar 28 only needs to be in the shape of a ring surrounding the radiation part 8, and the shape of the ring may be an ellipse or a circular shape. Can be a polygon such as a square.

[Third modified example]

As shown in FIG. 8 , in the antenna device 2 of the third modified example, the concavo-convex portion 20 provided on the outer wall surface 4 around the radiation portion 8 is composed of a plurality of slopes 32 formed on the radiation portion 8 side. The highest part with the highest height, and the lowest part with the lowest height on the side opposite to the radiation part.

The plurality of slopes 32 are each formed such that the height continuously changes from the highest part to the lowest part. Each slope 32 is formed in a straight line parallel to the central axis O of the waveguide 10 , and each slope 32 is arranged so as to continuously expand in the X-axis direction.

In other words, in the antenna device 2 of this modified example, the outer wall surface 4 around the radiation portion 8 is a reflection surface that changes in a zigzag shape like a Fresnel lens. Furthermore, the width in the X-axis direction of the plurality of slopes 32 constituting the reflection surface is set to be equal to or greater than λ/2, and the width becomes longer as the slope approaches the radiation portion 8 .

Even if the concavo-convex portion 20 is constituted by a plurality of continuous inclined surfaces 32, by adjusting the width of the inclined surfaces 32 and the height from the lowest part to the highest part, the reflection direction of the radio wave from the outer wall surface 4 around the radiation part 8 can be set to a different direction. An arbitrary direction different from the Z-axis direction is set.

Therefore, also in the antenna device 2 of this modified example, similar to the above-mentioned first embodiment and the first and second modified examples, it is possible to suppress the gap between the outer wall surface 4 of the antenna device 2 and the object 50 arranged forward in the radiation direction. , resulting in overlapping reflections.

[Fourth modified example]

As shown in FIG. 9 , in the antenna device 2 of the fourth modified example, the concave-convex portion 20 is composed of a plurality of slopes 38 as in the third modified example. The plurality of slopes 38 are formed in an annular shape so as to surround the entire area around the radiation portion 8 , and each slope 38 is disposed so as to continuously expand around the radiation portion 8 as a center.

Even if the concavo-convex portion 20 is constituted by a plurality of annular slopes 32 in this way, similarly to the antenna device 2 of the third modified example, by adjusting the width and height of the slopes 32, the outer wall surface around the radiation portion 8 can also be adjusted. The reflection direction of the radio wave in 4 is set to an arbitrary direction different from the Z-axis direction.

Therefore, also in the antenna device 2 of this modified example, as in the above-mentioned first embodiment and the first, second, and third modified examples, it is possible to suppress the gap between the outer wall surface 4 of the antenna device 2 and the antenna device arranged forward in the radiation direction. Between the objects 50, overlapping reflections are generated.

In addition, in this modified example, the plurality of slopes 38 constituting the concave-convex portion 20 do not necessarily have to be formed in an annular shape. Like the protrusions 28 in the second modified example, the shape of the ring can also be an ellipse, or Can be a polygon such as a square.

[Second Embodiment]

As shown in FIG. 10 , the waveguide slot antenna of this embodiment is the same as the first embodiment, and is an antenna device 2 used in a millimeter-wave radar device mounted on an automobile or the like, and includes a plurality of waveguide slot antennas as shown in FIG. 2 . wave tube10.

Furthermore, the outer wall surface 4 around the radiation portion 8 constituted by the slits 6 provided in the plurality of waveguides 10 is provided at an angle of 45 degrees with respect to the Y-axis along the central axis O of the waveguide 10 . The plurality of linear projections 42 are provided obliquely at predetermined intervals.

In other words, in this embodiment, the concave-convex portion 20 is formed by a plurality of protrusions 42 provided at an inclination angle of 45 degrees with respect to the Y-axis and the X-axis and the grooves 44 sandwiched between the protrusions 42 .

In this concave-convex portion 20 , the widths in the alignment direction of the protrusions 42 and the grooves 44 are set to one-half (λ/2) of the wavelength (λ) of the center frequency of radio waves transmitted and received by the antenna device 2 . In addition, the depth of the groove portion 44 is set to 3·λ/2+n·λ (where n is an integer).

In the antenna device 2 of the present embodiment configured in this way, when the linearly polarized radio wave radiated from the radiation section 8 collides with the object 50 and is reflected, and the reflected wave enters the antenna device 2 , the concave-convex section 20 makes the incident wave The plane of polarization is rotated 90 degrees and reflected.

In other words, as shown in FIG. 11 , when the electric field Win of the incident wave is divided into an electric field component WA parallel to the central axis of the groove portion 44 and an electric field component WB perpendicular thereto, the electric field component WA is in the groove portion 44. , is reflected with the same phase regardless of the depth of the groove portion 44 .

On the other hand, since the width of the groove 44 is λ/2, the electric field component WB is reflected in the groove 44 and causes phase rotation together with the reflection from the protrusion 42 . As a result, by setting the depth of the groove portion 44 as described above, the electric field component WB is reflected in an opposite phase, and the reflection component WBR and the reflection of the electric field component WA are synthesized.

Therefore, as shown in FIG. 10, the linearly polarized electric wave radiated from the antenna device 2 collides with the object 50 and is reflected, and the incident wave incident to the antenna device 2 rotates the plane of polarization by 90 degrees at the concave-convex portion 20 provided on the outer wall surface 4. and reflect.

For example, FIG. 12A and FIG. 12B show that the radio waves of the same polarization plane as the linearly polarized radio waves radiated from the radiation part 8 are incident on the antenna device without the concave-convex part 20 on the outer wall surface 4 and the antenna device 2 of this embodiment, and the measurements are made. The measurement result of the power of the reflected wave.

As shown in FIG. 12A, in the antenna device having no concavo-convex portion 20 on the outer wall surface 4, the reflected power of the reflected wave having the same polarization plane as the incident wave, that is, the main polarization component, and the orthogonal polarization in which the polarization plane is rotated by 90 degrees relative to the main polarization The reflected power of the component is significantly improved compared to that.

On the other hand, in the antenna device 2 of the present embodiment, as shown in FIG. 12B , the reflected power of the main polarization component is significantly reduced near the reflection angle 0 [deg.] compared to the antenna device without the unevenness 20, The reflected power of the orthogonal polarization components rises to the same level as the reflected power of the main polarization.

Therefore, it can also be seen from this measurement result that the incident wave incident on the antenna device 2 is reflected while the polarization plane is rotated by 90 degrees at the concavo-convex portion 20 provided on the outer wall surface 4 .

Therefore, in the antenna device 2 of the present embodiment, even if the reflected wave from the outer wall surface 4 of the antenna device 2 collides with the object 50 and is reflected, the antenna device 2 enters a radio wave whose polarization plane is rotated by 90 degrees relative to the radio wave that can be received. .

Thus, according to the antenna device 2 of the present embodiment, it is possible to suppress reception of reflected waves at the antenna device 2 due to overlapping reflections between the object 50 and the antenna device 2 that are forward in the radiation direction.

Therefore, even if superimposed reflection occurs between the object 50 ahead in the radiation direction and the antenna device 2, it is not affected by the superimposed reflection, but the reflected wave from the target object outside the vehicle to be detected can be received, and the radar device can be suppressed. The detection accuracy of the target object is reduced.

In addition, in the antenna device 2 of the present embodiment, there is no need to provide a filter such as the above-mentioned frequency selective surface unit in order to suppress the occurrence of superimposed reflections, so similar to the first embodiment, it is possible to suppress The transmission and reception characteristics of the antenna device 2 deteriorate.

In addition, although in this embodiment, the protrusions 42 constituting the concavo-convex portion 20 are provided to be inclined at an angle of 45 degrees with respect to the Y-axis along the central axis O of the waveguide 10, this is for The outer wall surface 4 rotates the polarization plane of the incident wave by 90 degrees and reflects it.

However, as long as the polarization plane of the incident wave is rotated, the power of the reflected wave caused by overlapping reflection received by the radiation section 8 can be reduced. Therefore, the inclination angle of the protrusion 42 with respect to the Y axis does not necessarily need to be 45 degrees, and may be It can be changed appropriately.

[Other Embodiments]

The embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments, and can be implemented with various modifications.

For example, in the above-described embodiment, the antenna device 2 as a waveguide slot antenna includes a plurality of waveguides 10 in which a plurality of slits 6 are arranged in a row in the direction of the central axis, and each waveguide The case where the plurality of waveguides 10 are arranged side by side in a direction perpendicular to the central axis of 10 will be described as an example.

However, even if it is an antenna device including a waveguide 10 in which a plurality of slits 6 are arranged in a row in the direction of the central axis, the technology of the present disclosure can be applied in the same manner as in the above-mentioned embodiment or modified example, and the same Effect.

In addition, in the above-mentioned embodiment, the case where the antenna device 2 as a waveguide slot antenna is used in a radar device for object object detection installed in an automobile or the like has been described as an example. However, the waveguide of the present disclosure The slot antenna can also be applied to communication devices and the like that perform wireless communication.

Moreover, if the antenna device of this embodiment is applied to a communication device, it is possible to suppress the reflected waves reflected from an object such as a radome arranged in front of the radiation direction from being overlapped and reflected between the antenna device and the object, and the communication accuracy of the communication device reduce.

In addition, the shape and size of the concavo-convex portion 20 described in each of the above-mentioned embodiments are examples, and in the antenna device 2, as long as the reflection characteristic that can suppress the influence of overlapping reflection can be obtained, it can be suitably change.

In addition, the antenna device 2 may be configured by appropriately combining the shapes of the concavo-convex portions 20 of the above-described embodiments and providing them on the outer wall surface 4 .

Claims (14)

1. A waveguide slot antenna, wherein: The waveguide (10) is provided with a plurality of slits (6) arranged at predetermined intervals in the direction of the central axis as radiation portions (8) for radiating radio waves; and The concavo-convex part (20) is provided on the outer wall surface (4) around the above-mentioned radiation part in such a manner as to periodically expand from the above-mentioned radiation part, The concavo-convex portion is configured to reflect an incident wave incident from the front of the radiation direction of the radio wave from the radiation portion in a direction different from the incident direction of the incident wave. 2. The stilling pipe slot antenna according to claim 1, wherein, providing a plurality of the waveguides, the plurality of waveguides being arranged side by side in such a manner that the radiation portions are arranged in a direction perpendicular to the central axis of each waveguide, The concavo-convex portion is provided so as to surround the radiation portion of the plurality of waveguides. 3. The stilling pipe slot antenna according to claim 1 or claim 2, wherein, The width of the concave portion between the convex portions among the concave-convex portions periodically provided on the outer wall surface of the waveguide is set to the wavelength (λ) of the radio wave radiated from the waveguide slot antenna. More than one-half of (λ/2). 4. The stilling pipe slot antenna according to claim 3, wherein, The concave-convex portions periodically provided on the outer wall surface of the waveguide are set so that the width of the periodic array direction of the concave-convex portions is one-half of the wavelength (λ) of the above-mentioned radio wave in the concave portion and the convex portion, respectively. (λ/2). 5. The waveguide slot antenna according to any one of claims 1 to 4, wherein, The concave-convex portion includes a plurality of protrusions (22) and grooves (24) sandwiched by the protrusions, and the protrusions are formed in a straight line so as to be parallel to the central axis of the waveguide in which the plurality of slits are arranged. shape. 6. The waveguide slot antenna according to any one of claims 1 to 4, wherein, The concave-convex part includes a plurality of protrusions (26) and a groove part (24) sandwiched by the protrusions, and the plurality of protrusions are respectively arranged in the axial direction parallel to the central axis of the waveguide in which the plurality of slits are arranged and with the groove part (24). The above-mentioned central axis is dispersedly arranged at predetermined intervals in the axial direction perpendicular to the central axis. 7. The waveguide slot antenna according to any one of claims 1 to 4, wherein, The concavo-convex part includes a plurality of protrusions (28) and grooves (24) sandwiched by the protrusions, and the protrusions are formed in an annular shape so as to surround the radiation part of the waveguide. 8. The stilling pipe slot antenna according to claim 1 or claim 2, wherein, The concave-convex portion includes a plurality of inclined surfaces (32, 38), and the plurality of inclined surfaces are configured such that the side of the radiation portion is the highest highest portion, and the side opposite to the radiation portion side is the lowest lowest portion, and the height is from the above-mentioned The highest portion varies continuously throughout the lowest portion and extends from the radiating portion. 9. The stilling pipe slot antenna according to claim 8, wherein, The plurality of slopes are arranged in a zigzag shape so as to extend continuously from the radiating portion, and the width of each slope in the arrangement direction is set to half the wavelength (λ) of the radio wave radiated from the waveguide slot antenna. One (λ/2) or more. 10. The stilling pipe slot antenna according to claim 8 or claim 9, wherein, The plurality of slopes are each formed in a straight line so as to be parallel to the central axis of the waveguide in which the plurality of slits are arranged. 11. The stilling pipe slot antenna according to claim 8 or claim 9, wherein, Each of the plurality of slopes is formed in an annular shape so as to surround the radiation portion of the waveguide. 12. A waveguide slot antenna, wherein: The waveguide (10) is provided with a plurality of slits (6) arranged at predetermined intervals in the direction of the central axis as radiation portions (8) for radiating radio waves; and A plurality of linear projections (42) are provided at intervals on the outer wall surface around the radiation portion so as to be inclined at a predetermined angle with respect to the central axis of the waveguide, The above-mentioned plurality of protrusions are configured to pass through each protrusion and the groove portion (44) sandwiched by the protrusions, so that the incident wave of the radio wave from the above-mentioned radiation part that is incident from the front of the radiation direction is rotated to rotate the polarization plane of the incident wave. Reflect at a specified angle. 13. The stilling pipe slot antenna according to claim 12, wherein, A plurality of the waveguides are provided, and the plurality of waveguides are arranged side by side in such a manner that the radiation parts are arranged in a direction perpendicular to the central axis of each waveguide, The plurality of protrusions are arranged around the radiation portions of the plurality of waveguides. 14. The stilling pipe slot antenna according to claim 12 or claim 13, wherein, The plurality of protrusions are provided around the radiating portion so as to be inclined at 45 degrees with respect to the central axis of the waveguide, In the above-mentioned plurality of protrusions and the above-mentioned groove portion, the width of the arrangement direction of the plurality of protrusions is set to be one-half (λ) of the wavelength (λ) of the radio wave radiated from the waveguide slot antenna. /2), the depth of the groove portion is set to 3·λ/2+n·λ, where n is an integer.

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